Preserving nerves in operations play important roles in the QOL (quality of life) of patients, as well as preserving organ functions. Hitherto, in order to determine the position of thin nerves, a staining technology using a dye has been improved. However, the staining itself is harmful to humans in most cases, and hence it is difficult to use the staining for observation during operations. Therefore, only thick nerves that can be observed with naked eyes of operators or with white light imaging using an image sensor have been mainly targeted for nerve preservation. There is no technology for determining the position of thin nerves, and hence the determination of the position of nerves has no choice but to depend on the anatomical knowledge, that is, the experience of operators.
Myelinated nerves can still be detected by Raman scattering spectroscopy due to the presence of a myelin sheath rich in lipid. A Raman band derived from lipid (myelin) is to be measured in the myelinated nerves. Therefore, it is difficult to apply this measurement to unmyelinated nerves lacking a myelin sheath, and thus the comprehensive detection of nerves has not been realized.
In contrast, Raman scattering spectroscopy is a form of vibrational spectroscopy. This method provides direct information on specific molecular vibration of chemical bonds in molecules. In Raman scattering spectroscopy, incident light and molecular vibration interact with each other, and thus specific energy changes depending on the molecular vibration can be plotted as a spectrum, thus allowing identification of a substance without staining. Substance detecting methods, imaging methods, and devices that utilize such characteristics of Raman scattering spectroscopy have been developed (Patent Literatures (PTL) 1 and 2). Recent research using Raman scattering spectroscopy in the medical field has focused on tissue diagnosis, such as the diagnosis of cancer (Non-patent Literature (NPL) 1), atherosclerosis (Non-patent Literature (NPL) 2), and oxygen saturation of hemoglobin (Non-patent Literature (NPL) 3). Patent Literature (PTL) 3 discloses a method involving distinguishing and imaging myocardial tissue and blood vessels, and collagen-rich regions. However, none of Non-patent Literatures and Patent Literatures have attempted to detect nerves comprehensively.